The distribution and relative ecological roles of autotrophic and heterotrophic diazotrophs in the McMurdo Dry Valleys, Antarctica

Kathryn J Coyne; Alexander E Parker; Charles K Lee; Jill A Sohm; Andrew Kalmbach; Troy Gunderson; Rosa León-Zayas; Douglas G Capone; Edward J Carpenter; S Craig Cary

doi:10.1093/femsec/fiaa010

The distribution and relative ecological roles of autotrophic and heterotrophic diazotrophs in the McMurdo Dry Valleys, Antarctica

FEMS Microbiol Ecol. 2020 Mar 1;96(3):fiaa010. doi: 10.1093/femsec/fiaa010.

Authors

Affiliations

¹ College of Earth, Ocean, and Environment, University of Delaware, Lewes, DE 19958, USA.
² Estuary and Ocean Science Center, San Francisco State University, Tiburon, CA 94920, USA.
³ International Centre for Terrestrial Antarctic Research, School of Science, University of Waikato, Hamilton 3240, New Zealand.
⁴ Wrigley Institute for Environmental Studies and Department of Biological Sciences, University of Southern California, Los Angeles, CA 9008-037, USA.
⁵ Department of Biological Sciences, University of Southern California, Los Angeles, CA 9008-037, USA.
⁶ Willamette University, Biology Department, Salem, OR 97301, USA.

Abstract

The McMurdo Dry Valleys (MDV) in Antarctica harbor a diverse assemblage of mat-forming diazotrophic cyanobacteria that play a key role in nitrogen cycling. Prior research showed that heterotrophic diazotrophs also make a substantial contribution to nitrogen fixation in MDV. The goals of this study were to survey autotrophic and heterotrophic diazotrophs across the MDV to investigate factors that regulate the distribution and relative ecological roles of each group. Results indicated that diazotrophs were present only in samples with mats, suggesting a metabolic coupling between autotrophic and heterotrophic diazotrophs. Analysis of 16S rRNA and nifH gene sequences also showed that diazotrophs were significantly correlated to the broader bacterial community, while co-occurrence network analysis revealed potential interspecific interactions. Consistent with previous studies, heterotrophic diazotrophs in MDV were diverse, but largely limited to lakes and their outlet streams, or other environments protected from desiccation. Despite the limited distribution, heterotrophic diazotrophs may make a substantial contribution to the nitrogen budget of MDV due to larger surface area and longer residence times of lakes. This work contributes to our understanding of key drivers of bacterial community structure in polar deserts and informs future efforts to investigate the contribution of nitrogen fixation to MDV ecosystems.

Keywords: Antarctica; McMurdo Dry Valleys; co-occurrence network; cyanobacteria; heterotrophic diazotrophy.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Antarctic Regions
Autotrophic Processes
Ecosystem*
Heterotrophic Processes*
Nitrogen Fixation
RNA, Ribosomal, 16S / genetics

Substances

RNA, Ribosomal, 16S